There can't be a practical reason for believing something that is not true.

To the young I should offer two maxims: Don't accept superficial solutions of difficult problems. It is better to do a little good than much harm. I should not offer anything more specific; every young person should decide on his or her own credo.

Science, in its ultimate ideal, consists of a set of propositions arranged in a hierarchy, the lowest level of the hierarchy being concerned with particular facts, and the highest with some general law, governing everything in the universe. The various levels in the hierarchy have a two-fold logical connection, travelling one up, one down; the upward connection proceeds by induction, the downward by deduction.

The axiomatic method has many advantages over honest work.

The first step in a fascist movement is the combination under an energetic leader of a number of men who possess more than the average share of leisure, brutality, and stupidity. The next step is to fascinate fools and muzzle the intelligent, by emotional excitement on the one hand and terrorism on the other.

The Ten Commandments should be headed like an examination paper: No more than six to be attempted.

Never try to discourage thinking, for you are sure to succeed.